Re: [Qemu-devel] Qemu and heavily increased RSS usage

[Peter Lieven <pl@kamp.de>]

Am 23.06.2016 um 18:53 schrieb Paolo Bonzini:
>
> On 23/06/2016 18:19, Peter Lieven wrote:
>> Mhh, so your idea could be right. But what to do now? The introduction
>> of RCU obviously increases the short term RSS usage. But thats never
>> corrected as it seems.
>>
>> I see this behaviour with kernel 3.19 and kernel 4.4
> If it's 10M nothing.  If there is a 100M regression that is also caused
> by RCU, we have to give up on it for that data structure, or mmap/munmap
> the affected data structures.

If it was only 10MB I would agree. But if I run the VM described earlier
in this thread it goes from ~35MB with Qemu-2.2.0 to ~130-150MB with
current master. This is with coroutine pool disabled. With the coroutine pool
it can grow to sth like 300-350MB.

Is there an easy way to determinate if RCU is the problem? I have the same
symptoms, valgrind doesn't see the allocated memory. Is it possible
to make rcu_call directly invoking the function - maybe with a lock around it
that serializes the calls? Even if its expensive it might show if we search at the
right place.

Thanks,
Peter